What I think is causing this ? Well it's relatively simple. To have the none public version here, you need to find someone who have this version and decide to share it.
In the past it worked because the amount of game was, relatively speaking, limited. Finding someone who was a patron of "this" dev, or was interested enough in the game to search it elsewhere, then kind enough to share it with us, was easier.
But nowadays you can easily have more than 50 new games during a single month. Those kind people have limited funds and limited times, they can't pledge for too many games, nor search too many of them elsewhere. Of course, the number of members here also raised considerably, but most of them come for the free games, not for the sharing spirit.
You can see it not only by the lack of none public updates, but also by the gap between the version released here for some games. Even when the updates are public, they aren't all shared here.
In a community, every one have to take his share of the job for it to works. So, instead of complaining about authors who don't end releasing all their updates publicly, do your part, and get/find the private updates and share them with us. Obviously, you don't have to do it for all the games, but if only 0.01% of the members were doing it for just 3 or 4 games, you would find all the updates.
And you can do it while still caring about the author interest, by example by waiting one week before leaking the update.
